№3. Сократите: 1) \(\frac{12\cdot21}{35\cdot15}\); 2) \(\frac{72\cdot11}{33\cdot30}\); 3) \(\frac{25\cdot17\cdot44}{51\cdot8\cdot75}\).

Сокращаем общие множители в числителе и знаменателе.

1. \(\frac{12\cdot21}{35\cdot15}=\frac{4\cdot7}{5\cdot5}=\frac{28}{25}\).
2. \(\frac{72\cdot11}{33\cdot30}=\frac{12\cdot11}{11\cdot5}=\frac{12}{5}\).
3. \(\frac{25\cdot17\cdot44}{51\cdot8\cdot75}=\frac{25\cdot17\cdot11}{51\cdot2\cdot75}=\frac{11}{18}\), поскольку \(25/75=1/3\), \(17/51=1/3\), а \(44/8=11/2\).

Ответ: 1) \(\frac{28}{25}\); 2) \(\frac{12}{5}\); 3) \(\frac{11}{18}\).